Steam engines use steam as its working fluid to perform mechanical work. Steam engines include a boiler (also referred to as a steam generator) and a motor as its main components.
Commonly, combustible materials are burned, so as to boil water to create steam. Two main types of boilers are used, namely, a water-tube boiler and a fire-tube boiler. In the case of a water-tube boiler, hot gases created from combustion surround tubes that have water therein. In the case of a fire-tube boiler, hot gases created from combustion travel through tubes that are surrounded by water.
High pressure steam is delivered to the motor, which may include one or more cylinders. When the steam enters a cylinder, it expands and causes a piston inside the cylinder to move. Accordingly, chemical energy from the combustible materials is converted into heat energy in the form of hot gases, which is converted into kinetic energy in the form of steam, which is then converted into mechanical energy through use of the pistons inside the motor. Unfortunately, in steam engines, much of the heat is discarded without being converted into useful mechanical energy.
Furthermore, the water used in steam engines creates many problems. For example, inconveniently, both a fuel tank and a water tank must be replenished (e.g., filled—assuming fuel in a liquid form). As a point of reference, one version of a Stanley Steamer automobile of the early 1900's consumed approximately the same amount of fuel per mile as it did water.
Another problem with using water in steam engines is the need to locate sources of water to refill the water tank. It should be noted that the inventor recognizes that a condenser allows one to travel further without refilling a water tank. However, a significant amount of heat is still wasted with condensers.
Yet another problem of using water in steam engines is that it requires designers to determine how to prevent water from freezing in colder climates. For example, water may need to be mixed with additives to ensure that it has a lower freezing temperature than 0 degrees Celsius.
Yet a further problem is that the boiler must use materials that are somewhat heavy to be able to safely contain its high operating pressures. In addition, the boiler must have a sufficiently large surface area to properly transfer the heat created from combustion, so as to produce steam from water, which also adds to its overall weight.
Yet an even further problem is that water (or steam) promotes corrosion in both the boiler and motor. In addition, water is not compatible with the oil used in the lubrication system of an engine.
Despite all of the aforementioned problems with steam engines, there are several important benefits of steam engines as opposed to conventional (internal combustion) engines which burn fuel in their cylinders. Specifically, a boiler can burn fuel at a leaner mixture than a conventional engine. Accordingly, the fuel is oxidized better, which allows for more complete combustion. Furthermore, fuel and air can be burned at a much higher temperature in a boiler, which also provides a more complete combustion.
For a variety of reasons, internal combustion engines replaced steam engines to power automobiles. Like steam engines, much of the heat generated in internal combustion engines is wasted.
When fuel is burned in an internal combustion engine, the heat must be created and used in a very short time. In the case of a naturally aspirated internal combustion engine operating at 2000 RPM, the power stroke lasts approximately one sixteenth of a second. As a result, much of the fuel passes into the exhaust unburned or partially burned, which creates carbon monoxide.
In addition, there are harmful compounds created when fuel and air are ignited under pressure. Oxides of nitrogen form more easily in an ignited and compressed fuel/air mixture than they do when burned at atmospheric pressure.
Furthermore, a modern automobile uses a catalytic converter to burn some of the fuel that exhausts from the engine unburned. This reduces some of the pollutants, but the heat created in the process, along with the fuel that passes through the catalytic converter unburned, is not converted into useful work and is simply wasted.
In view of the above, it would be desirable to develop a heat exchanger for an engine that increases efficiency as compared to prior systems.